Conventional drainage and septic systems typically include underground components which require periodic access for cleaning or servicing. Most notably, septic tanks are typically pumped out every few years or even, in some cases, annually or more frequently. Other components of septic systems such as distribution boxes also often require periodic servicing. In order to gain access to such underground components, workers commonly use metal rods or the like to first locate the component and then they must remove the dirt above the component which is labor-intensive. Often, workers must remove dirt over a fairly wide area to correctly locate the lid of the component, or an access opening in the lid. Obviously, the conventional methods of locating and gaining access to underground drainage and septic components is time consuming and expensive. In addition, there has been a general trend by states and municipalities to require grade level access to underground components, so as to prevent such components from becoming "lost" which frequently occurs.
Attempts have been made to remedy the above problems by providing grade level access and a passageway between grade level and the underground component. Such attempts have often been make-shift assemblies roughly put together in the field. In one known example, clay tile or cement chimney flues have been positioned over a septic tank to provide a passageway between the septic tank and grade level. Such attempts have been less than successful in that ceramic chimney flues often have predetermined lengths of a foot or more, and such components are not easily length-adjustable, i.e. cutting a flue component is time-consuming, expensive and requires specialized tools. Chimney flues are also expensive, and such tile or cement components are also heavy and difficult to handle which leads to labor-intensive and expensive installation.
Another known prior art attempt at creating a crude riser was advertised for sale by American Manufacturing Company, Inc., Manassas, Va., in an October 1989 catalog. That construction was specifically aimed at providing a riser for use with septic system distribution boxes. The so-called "riser" was actually another distribution box unit in which, after first cutting out its bottom, that modified narrow bottom was simply fitted into an opening formed in the wider top of the actual distribution box, so as to create a make-shift riser having a height of about 14 inches. In effect, the user had to cut out the bottom and top of an expensive distribution box to form a riser. Such a construction had many shortcomings including the time-consuming installation process of cutting the top and bottom out of the distribution box to form a riser. For example, distribution boxes are relatively expensive components, and also, their rather flimsy thin-walled construction is unsuitable for holding up under the high weight-bearing loads normally applied to a riser structure at grade level, i.e. garden tractors and even pick-up trucks. The American manufactured type distribution box riser also has a predetermined height of about 14 inches, which excessive height is impractical to adjust from a standpoint of difficulty in cutting the device, plus the fact that a cut edge in a drop box does not readily accept a preformed lid or grade level access cover. A significant shortcoming of this particular prior art riser construction is that the American manufactured distribution box has angled side walls, which walls inefficiently distribute the weight placed on the top riser to the bottom distribution box, often resulting in breakage. This weight-bearing load capacity factor is an important consideration when it is considered that, at best, people and 1000 pound riding mowers will pass over the grade level access lid and, at worse, heavier vehicles such as pickup trucks may drive over the lid.
An important aspect of the present invention therefore lies in providing a unique stackable riser formed of light-weight plastic which is usable to form a height-adjustable grade level access for underground components and which forms a rigid structure capable of supporting heavy loads applied to the grade level access lid. A suitable cover means such as an imperforate cover or a drain grate is used to seal the uppermost stackable riser in the vertical riser tower. The injection-molded plastic stackable risers are lightweight and easy to handle. A plurality of such risers can be used to easily, simply and efficiently form a vertical passageway and grade level access above an underground drainage or waste system component.
In brief, the stackable riser of this invention includes a continuous peripheral side wall having outer and inner surfaces and having a first free edge portion and a second edge portion. The side wall of the riser extends in a substantially perpendicular direction with respect to a horizontal plane. The first free edge portion defines a first end opening, and the second edge portion is provided with a U-shaped connecting member which forms an oppositely-facing second end opening. The U-shaped connecting member includes a transverse intermediate portion and first and second generally perpendicular dependent legs which define a channel which is shaped to receive a first free edge portion of another riser. The riser is stackable with other risers to form a riser combination in which the first free edge portions of the risers are interconnected with the U-shaped connecting members of the adjacent risers.
The inner and outer surfaces of the side wall are preferably provided with vertically-extending ribs for strengthening the side wall. However, the inner ribs further include terminal edges which form shoulders positioned a predetermined distance away from the tip of the first free edge portion of the side wall. These shoulders form a ledge for receiving the first dependent leg of the U-shaped connecting member of an adjacent riser so that the first dependent legs and inner ribs of a riser stack all extend along a common vertical axis for efficiently transmitting weight-bearing loads through the entire riser stack. Each of the risers is also preferably provided with a horizontally-extending rib for reinforcing the riser unit's side wall. A horizontally-extending rib preferably extends outward from the intermediate portion of the U-shaped connecting member.
In one embodiment, the peripheral side wall of the riser includes four sidewall sections which form a generally square or rectangular-shaped riser having four internal corners on the inner surface of the side wall. Each of the corners is provided with a vertically-extending attachment member which includes a shoulder positioned to receive a screw for facilitating attachment of cover means to the riser. In order to allow for selective vertical height adjustment between the underground component and grade level, the side wall of each riser preferably has a vertical height of approximately 3 to 7.5 inches, and preferably 6 inches, so that no cutting of the risers is required.
When a plurality of stackable risers of this invention are stacked together, the side walls of each riser are stacked directly on top of each other and extend along a first common vertical axis for efficiently transmitting weight-bearing loads through the vertical stack. In addition, the first dependent leg of the U-shaped attachment member and the inner ribs also extend along a second common vertical axis for efficiently transmitting loads through the stack. The stackable riser of this invention in usable in combination with underground components such as septic tanks, distribution boxes, or drop boxes.
In the combination of the stackable riser and a distribution box, the distribution box includes angled side walls, a transverse peripheral shoulder extending from a top of the side walls, and a vertically-extending flange. The flange is shaped to be received within the channel formed by the U-shaped connecting member of the risers. When the risers are connected to the distribution box, the side wall of the first riser is positioned directly above the flange of the distribution box. In use, the transverse shoulder of the distribution box extends outward over backfill so that weight-bearing loads which act upon the vertical stack of risers is transmitted directly through the side walls of the risers and the flange of the distribution box to the backfill, thereby transferring the load away from the angled side walls of the distribution box which might otherwise undesirably result in breakage.
Cover means are provided for attachment to the uppermost riser of the riser stack and covering the vertical passageway formed by same. The cover means may take the form of an imperforate cover or a drain grate, which might be desirable in some applications. The imperforate cover of this invention includes a peripheral U-shaped attachment portion which includes a transverse intermediate portion and first and second depending legs and which defines a channel shaped to receive the top free edge of a riser. A dome-shaped cover plate portion connects to the transverse intermediate portion of the U-shaped attachment portion. The U-shaped attachment portion of the cover may be substantially similar to, or the same as, the U-shaped connecting portion of the stackable risers of this invention.
The imperforate cover is preferably provided with a centrally located circular rib on an inner surface of the dome-shaped plate portion and a plurality of radially-spaced ribs extend between the circular rib portion and the first depending leg of the U-shaped connection portion. Such an arrangement of ribs effectively forms a strong weight-bearing cover which efficiently transfers any weight-bearing loads through the side walls of the risers in the vertical stack and directly to the septic tank, distribution box or other underground component.
Other features, objects and advantages of the invention will become apparent from the following drawings and description.